1. Field of the Invention
The present invention relates to a fastener, in particular to a versatile fastener that provides a preferable stability at the time of fastening and favorably decreases the screwing torque as well as the resistance.
2. Description of the Related Art
A conventional screw 1 shown in FIG. 1 generally comprises a shank 11, a head portion 12 disposed at one end of the shank 11, and a plurality of threads 13 spirally disposed on the shank 11. A free end 14 is formed at the other end of the shank 11. The free end 14 includes a guiding area 141 defined on the surface thereof as well as extensively formed in the connection with the threads 13, and a cutting edge 142 defined on a congregation formed by the guiding area 141, the free end 14, and the threads 13. In applying the screw 1 for fastening, the free end 14 of the screw 1 is propped against an object. Thence, the free end 14 leads the entire screw 1 to gradually screw into the object 2. The cutting edge 142 drills and chips the object 2, and the guiding area 141 guides the debris generated from the drilling. Accordingly, the screw 1 achieves the fastening and fixing function.
However, in practice, the conventional screw 1 merely utilizes the guiding area 141 and the cutting edge 142 formed on the free end 14 to implement the cutting and the debris guidance. Since, an included angle formed on the guiding area 141 is rather small, the accommodating area accordingly defined thereby is relatively confined. Asa result, the debris generated at the time of screwing is readily retained in the guiding area 141, hence incurring a poor guiding effect. Moreover, such a screw 1 merely causes the threads 13 to provide multiple supporting points engaging the object 2. Therefore, if a rotating force is continuously executed on the screw 1, the debris will be adversely compressed in view of the unfavorable guiding effect. Additionally, the object 2 will readily sway because of the insufficient supporting force. As a result, the object 2 readily splits due to the overlarge screwing torque. The screw 1 also fails to provide a speedy screwing and influences the screwing effect.
Another conventional screw 3 is disclosed for removing the disadvantages of the conventional screw 1. Referring to FIG. 2, the screw 3 comprises a shank 31, a head portion 32, and a plurality of threaded portions 33 spirally disposed on the shank 31. A free end 34 is formed at one end of the shank 31, and a blank area 35 is formed between the threaded portion 33 and the free end 34. Further, a plurality of protruding ribs 351 are formed on the blank area 35. In screwing, the free end 34 is propped against an object 4, and thence the screw 3 is gradually screwed into the object 4 via a screwing force. By means of the protruding ribs 351 providing a reaming effect on the object 4, the screw 3 can succeed in achieving a swift drilling. Thence, a fastening and fixing effect is accomplished.
However, while the object 4 is reamed by the protruding ribs 351, the fibers of the object 4 are practically incompletely severed. As a result, the unsevered fibers adversely entangle the shank 31, thereby influencing the screwing speed of the screw 3. Therefore, a rather great driving force has to be further exerted on the screw 3 for smoothly screwing into the object 4. Consequently, the screw 3 has shortcomings which could be improved, i.e. a slower screwing speed, and a laborious screwing torque as well as a large resistance.